Various matters such as dust, pollen, tobacco smoke, breathed-out air and the like that are disagreeable or harmful to the human body are contained in air in a room (room air). Especially, in recent years, because houses are often closed completely, such harmful matters easily collect in a room. Accordingly, conventionally, windows of a room are sometimes opened for spontaneous ventilation. However, as a matter of fact, it is hard to carry out spontaneous ventilation as desired in an area where air pollution is serious, at home or in an office if there is a family member or a colleague who is suffering from hay fever. In such situation, an air cleaner that has an air cleaning function to clean room air is generally becoming widespread.
Generally, an air cleaner is equipped with an air filter on the front of its main body, and an air flow passage in which a blower is disposed is formed inside the main body. The air flow passage extends from an opening of the main-body front to an outlet of an upper portion of the main body. Such an air cleaner sucks room air, that is, outside air into the air flow passage through the air filter as the blower rotates, and sends out the sucked air into the room, that is, the outside through the outlet. Here, harmful matters contained in the air are caught, adsorbed, or decomposed by the air filter to be removed so that the air is cleaned.
Further, for the purpose of adjusting room air to obtain a more comfortable condition, some air cleaners have a humidifying function besides the air cleaning function. In an air cleaner having the humidifying function, a humidifying filter that contains water is so disposed as to close a portion of the sectional region of the air flow passage, and part of the air that is cleaned by the air filter absorbs water when it goes through the humidifying filter, thereby the air is humidified (e.g., see patent document 1).    [Patent document 1]: JP-A-2006-46729